Low cost, renewably-derived 2,5-furandicarboxylic acid (FDCA) and its derivatives harbor considerable potential for commercial applications. See, e.g., “Top Value Added Chemicals from Biomass,” Volume I—Results of Screening for Potential Candidates from Sugars and Synthesis Gas, produced by Staff at Pacific Northwest National Laboratory (PNNL), National Renewable Energy Laboratory (NREL), Office of Biomass Program (EERE); Eds. T. Werpy and G. Petersen (2003). In certain applications, they have the potential to displace aromatic dicarboxylic acids such as terephthalic and isophthalic acid. A. Corma, et al., Chem. Rev., 107:2411 (2007). FDCA and its derivatives are also useful in the production of other commodity chemicals. Id. For example, FDCA may be hydrogenated to adipic acid, which is utilized in the production of nylon. Id. Aromatic dicarboxylic acids are used for the production of polyesters and polyamides in the scale of tens of millions of tons per year. See, e.g., “Modern Polyesters: Chemistry and Technology of Polyesters and Copolyesters,” Eds. J. Scheirs and T. Long; Wiley (2013).
Methods of producing FDCA have been reported in the literature. For example, Corma, et al., report that FDCA can be produced by direct oxidation of 5-hydroxymethylfurfural (HMF) with nitric acid, though with low selectivity and yield. A. Corma, et al., supra. Verdeguer, et al. describe another process in which HMF is oxidized catalytically to FDCA using 5% Pt supported on carbon in the presence of sodium or potassium hydroxides with yields reported to be 70%. J. Mol. Catal. 85:327 (1993). They reported achieving FDCA yields of up to 80% using a 5% Pt/5% Pb catalyst formulation on carbon in the presence of 1.25 M base solution. Id. When the amount of base was reduced to a concentration of 0.1 M, the authors reported that no conversion of HMF to FDCA was achieved, suggesting high concentrations of base are an important requirement for achieving higher FDCA yields. See Id. In another reported method, Besson, et al., report that Pt/Bi catalysts supported on carbon can produce FDCA with close to 100% selectivity under reaction conditions of a high base (Na2CO3) to HMF ratio of 2 to 4. See WO 2014/122319. An ancillary result of adding a base (e.g., NaOH, KOH, Na2CO3) to the reaction is the formation of salts (e.g., sodium or potassium salts) of FDCA. The formation of FDCA salts may be advantageous given that FDCA salts are reported to be more water-soluble than FDCA itself, thereby affording the potential opportunity to carry out the conversion process at higher HMF concentrations. Id. However, a disadvantage of such salt production is the need for further processing (e.g., further separation and/or conversion of the salt form of FDCA to FDCA) in the recovery of FDCA.
U.S. Pat. No. 8,338,626 describes the production of FDCA and its esters by oxidation of mono- or dialkoxymethylfurfural in the presence of a homogeneous catalytic system that is similar to the system used in terephthalic acid production (Co/Mn/Br). The patent reports a maximum total yield of furandicarboxylics (with FDCA as a major constituent) of 82%. Id. U.S. Pat. No. 7,700,788 describes a method of HMF oxidation to FDCA under high oxygen (air) pressure using a 5% Pt/ZrO2 catalyst, prepared by a specific procedure from Pt acetylacetonate. In this process, HMF at a concentration of three weight percent, in the presence of base, and oxygen at a pressure of 150 psi resulted in the production of FDCA at a yield of 90%.
U.S. Pat. No. 4,977,283 describes the oxidation of HMF at concentrations around 10% in a base-free solution of water and diethylene glycol dimethyl ether in the presence of a Pt (5%) on activated carbon catalyst. The process provided only low yields (8%) of FDCA with the major product being 5-formylfuran-2-carboxylic acid.
In view of its potential as a biorenewable-derived replacement for petroleum-derived compounds that are used in the production of plastics and other materials, a commercially viable process for the production of large volumes of FDCA at high yields would be desirable.